The Impact of Late LHRH Agonist Dosing on Testosterone Suppression in Prostate Cancer Patients: An Analysis of US Clinical Data.

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The Journal of urology


PURPOSE: Evaluate timeliness of androgen deprivation therapy dosing, impact of dosing non-adherence on testosterone (T) and frequency of T/prostate-specific antigen (PSA) testing in prostate cancer (PCa) patients.

MATERIALS AND METHODS: Retrospective analyses of 22,860 PCa patients treated with luteinizing hormone-releasing hormone (LHRH) agonists. Analyses used two definitions of 'Month': '28 Day Month' ('Late': dosing after day 28, 84, 112, or 168) and 'Extended Month' ('Late' after day 32, 97, 128, or 194) for 1-, 3-, 4-, and 6-month formulations, respectively. Prevalence of 'Late' dosing, associated T values and frequency of T/PSA testing were assessed. Statistical significance was tested using unpaired t-test.

RESULTS: 84% of injections were 'Late' for '28 Day Month' and 27% for 'Extended Month'. For '28 Day Month', 60% and 29% of injections were 'Late' by >1 and >2 weeks. 4% of T were >50ng/dL for 'Early/On-Time' injections using both definitions. 15% and 27% of T were >50ng/dL when 'Late', for '28 Day Month' and 'Extended Month', respectively. For 'Early/On-Time' vs. 'Late', 22% vs. 31% of T were >20ng/dL for '28 Day Month' and 21% vs. 43% for 'Extended Month'. Mean T were higher when 'Late' (49ng/dL for '28 Day Month', 79ng/dL for 'Extended Month') vs. 'Early/On-Time' (21ng/dL for both). 83% of injections had PSA measurements, only 13% a T assessment.

CONCLUSIONS: LHRH agonists were frequently (84%) administered later than schedules used in pivotal trials. Nearly half of 'Late' T ('Extended Month') were >20ng/dL; mean T almost doubled castration level. Elevated T levels remain unidentified with infrequent testing.

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